Embodiments of the inventive concept described herein relate to a method of manufacturing a cathode active material and a cathode active material manufactured by the same, and more particularly, relate to a cathode active material which is rinsed by a compound including thiol group, includes residual sulfur on a surface, and having decreased residual lithium and a method of manufacturing the same.
A battery generates electrical power using materials which are capable of electrochemically reacting with each other at an anode and a cathode. A typical battery of such batteries includes a lithium secondary battery, which generates electrical energy by change of chemical potential when lithium ions are intercalated or deintercalated at an anode and a cathode.
The lithium secondary battery uses materials which are capable of being reversibly intercalated and deintercalated as an anode active material and a cathode active material, and is manufactured by being filled with an organic electrolyte or a polymer electrolyte between the anode and the cathode.
A lithium complex oxide is used as a cathode active material of the lithium secondary battery. A method of manufacturing the lithium complex oxide includes forming a precursor of transition metal, mixing the precursor of transition metal with a lithium compound, and plasticizing the mixture.
For Example, complex metallic oxides, such as LiCoO2, LiMn2O4, LiNiO2, and LiMnO2, used as the lithium complex oxide have been studied. LiCoO2 among the above compounds is excellent in cycle life and charge/discharge efficiency, thereby being used the most. However, structural stability is weak, and there is disadvantage in price competition since cobalt used as a base material is limited thereby being expensive.
A lithium manganese oxide, such as LiMnO2, LiMn2O4, is superior in thermal stability and in price. However, the lithium manganese oxide has a small capacity and is inferior in high temperature.
Furthermore, a LiNiO2 group cathode active material has high discharge capacity. However, synthesis of the LiNiO2 group cathode active material is difficult since cation mixing occurs between Li and transition metal, thereby being disadvantage in rate characteristics.
In addition, since Ni rich system which has Ni of 65% or more is cold reaction, residual lithium existing in LiOH or Li2CO3, which is remained on a surface of the cathode active material, is large in quantity. Such residual lithium i.e. unreacted LiOH or Li2CO3 reacts with an electrolyte in the battery to generate gas and to lead to swelling phenomenon, thereby lowering stability at high temperature. Furthermore, the unreacted LiOH or Li2CO3 may cause gelation since viscosity is increased when mixing the unreacted LiOH to form a slurry before forming an electrode plate.